Bioavailability overview

Mushak P. 1991. Gastro-intestinal absorption of lead in children and adults Overview of biological and biophysico-chemical aspects. Chemical Speciation and Bioavailability 3 87-104. 

The book focuses on the biogeochemistry of trace elements in arid and semiarid zone soils and includes an introductory chapter on the nature and properties of arid zone soils. It presents an updated overview and a comprehensive coverage of the major aspects of trace elements and heavy metals that are of most concern in the world s arid and semi-arid soils. These include the content and distribution of trace elements in arid soils, their solution chemistry, their solid-phase chemistry, selective sequential dissolution techniques for trace elements in arid soils, the bioavailability of trace elements, and the pollution and remediation of contaminated arid soils. A comprehensive and focused case study on transfer fluxes of trace elements in Israeli arid and semi-arid soils is presented. The book concludes with a discussion of a quantitative global perspective on anthropogenic interferences in the natural trace elements distributions. The elements discussed in this book include Cd, Cu, Cr, Ni, Pb, Zn, Hg, As, Se, Co, B, Mo and others. This book is an excellent reference for students and professionals in the environmental, ecological, agricultural and geological sciences. 

This chapter will review some of the important methods for carrying out in vivo absorption and bioavailability studies, as well as attempt to provide an overview of how the information may be used in the drug discovery process. The chapter is aimed at medicinal chemists and thus will focus on the use of animals in discovery phase absorption, distribution, metabolism, and excretion/pharmacokinetic (ADME/PK) studies, rather than the design of studies that are for regulatory submission, or part of a development safety package. 

Fig. 21.9. A short overview, from in silico to in vivo in humans, of methods available to investigate and predict fraction dose absorbed and bioavailability following oral dosing.

This volume gives an overview of the current status and an outlook to future more reliable predictive approaches. It is subdivided in five sections dealing with studies of membrane permeability and oral absorption, drug dissolution and solubility, the role of transporters and metabolism in oral absorption, computational approaches to drug absorption and bioavailability, and finally with certain drug development issues. 

Mangan FR, Flack JD, Jackson D. Preclinical overview of nabumetone. Pharmacology, bioavailability, metabolism, and toxicology. Am J Med 1987 83(4B) 6-10. 

Kramer J. The biopharmaceutics classification system—an overview of the current status in relation to IR and MR dosage forms. 1st International Conference on Bioavailability, Bioequivalence and Dissolution Testing, London, 2002. 

The scope is limited to issues relevant to the sources and bioavailability of DOM and the interface between DOM and several ecosystem-level processes such as nutrient/toxicant transformations and retention. This volume contains overviews of (1) the supply of DOM to aquatic ecosystems and variation in DOM composition, (2) processes mediating the transfer of... 

In this chapter we will provide a brief overview of the early approaches to bioavailability enhancement by use of simple lipid-based delivery systems (lipid solutions, emulsions etc), and then describe recent progress in the application of self-emulsifying- and microemulsion-based formulations. The effects of lipids on the oral bioavailability of co-administered poorly water-soluble drugs may also be classified from a mechanistic (and to a degree, historical) perspective as physicochemically mediated effects (solubility, dissolution, surface area) and biochemically mediated effects (metabolism, transport related events), and these will be approached separately. It is readily apparent, however, that in many cases physicochemically and biochemically mediated mechanisms will operate side by side. In some instances, bioavailability may also be enhanced by the stimulation of intestinal lymphatic transport, and these studies will be addressed in a separate section. 

As(V), and Hg(II) versus MMHg (monomethyl-Hg)], solubility [e.g., Fe(II) versus Fe(III) and Mn(II) versus Mn(IV)], the difference in volatility [Hg(0) versus Hg(II)], and bioavailability (e.g., labile-bound metal complex/strongly bound metal complex). It is therefore a challenge to identify and quantify the major species of elements such as Cr, Fe, Mn, As, and Fig in aquatic systems. Table 7.1 gives an overview of the levels of common trace metals in various aquatic systems. 

This chapter provides an overview of factors affecting dermal absorption. Factors influencing absorption are among others related to the skin (e.g. anatomical site, difference between species, metabolism, etc.) and the exposure conditions (e.g. area dose, vehicle, occlusion and exposure duration). In order to provide relevant information for the risk assessment of pesticides, dermal absorption studies should take these aspects into account. With respect to the methods being used nowadays for the assessment of dermal absorption, it is important to realize that neither in vitro nor in vivo animal studies have been formally validated. Available data from various in vitro studies, however, indicate that the use of the total absorbed dose (i.e. the amount of test substance in the receptor medium plus amount in the skin) could be used in a quantitative manner in risk assessment. Tape stripping of the skin can be adequate to give a good indication of test chemical distribution, and hence its immediate bioavailability. 

Despite their favourable properties, peptide-based drugs are under-represented in the pharmaceutical market. This discrimination is usually due to their poor bioavailability, which sometimes necessitates non-oral administration or even special medical devices such as inhalers. Another related major disadvantage of peptides is their low metabolic stability due to proteolytic degradation, hi addition, costs of goods for the drug substance are sometimes tremendous. Therefore, there is considerable interest to transform the active principle of biologically active peptides into small molecules with improved pharmacokinetic properties, hi this chapter, we present an overview of... 

Smith K. S. and Huyck H. L. O. (1999) An overview of the abundance, relative mobility, bioavailability, and human toxicity of metals. In The Environmental Geochemistry of Mineral Deposits Part A. Processes, Techniques and Health Issues (eds. G. S. Plumlee and M. J. Logsdon). Soc. Econ. Geol. Rev. Econ. Geol. 6A, Society of Economic Geologists, Littleton, pp. 29-70. 

It is generally accepted that the bioavailability of most topically applied drugs remains low. Various methods to increase this bioavailability have been used. One of the approaches is the use of absorption enhancers, and over the years, there has been a great interest in new chemical absorption enhancers. An absorption enhancer should be pharmacologically inert, non-toxic, have a rapid and reversible onset of action, be chemically and physically compatible with other formulation compounds, and be cosmetically acceptable. Of course not all absorption enhancers possess all of these characteristics, and a benefit-to-risk evaluation will determine the choice of a molecule as an absorption enhancer. The range of absorption enhancers that has been researched is large. Thus, overview of the most researched compounds is presented. 

Baggot J D 1992 Bioavailability and bioequivalence of veterinary drug dosage forms, with particular reference to horses an overview. Journal of Veterinary Pharmacology and Therapeutics 15 160-173 Dirikolu L, Lehner A F, Karpiesiuk W et al 2000 Identification of lidocaine and its metabolites in post-administration equine urine by ELISA and MS/MS. Journal of Veterinary Pharmacology and Therapeutics 23 215-222 Evans W E 1992 General principles of applied... 

Baggot J D 1992 Bioavailability and bloequivalence of veterinary drug dosage forms, with particular reference to horses an overview. Journal of Veterinary Pharmacology and Therapeutics 15 160-173 Freeman D E 1999 Gastrointestinal pharmacology. 

This chapter provides an overview of lycopene bioavailability and the potential benefits of dietary lycopene on human health. Lycopene chemistry and its effect on functionality will be discussed, followed by the effects of processing on lycopene obtained from tomatoes. Finally, methods of analysis and of extraction from tomatoes are discussed. 

From this brief overview of toxicity tests, their uses and methods of assessing their responses to toxic substances, it can be seen that this is a very complex topic with many unknowns and no single best way of addressing the problem of bioavailable toxicant estimation. In this chapter, an attempt will be made to describe some applications of toxicological data, how they could be analysed and how toxicity results could be integrated in ecological risk assessment frameworks. 

The chapters were selected to give a broad overview of the topic of bioavailability of iron with special emphasis on topics of concern to food producers. 

Artursson, P. and Tavelin, S. (2003) Studies of membrane permeability and oral absorption 6 Caco-2 and emerging alternatives for prediction of intestinal drug transport a general overview, in Drug Bioavailability - Estimation of Solubility, Permeability and Absorption (eds H. van de Waterbeemd, H. Lennernas and P. Artursson), Wiley, pp. 72-89. 

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